1. Field of the Invention
This invention relates to pumps and, in particular, to nonaerosol pump sprayers.
2. Description of the Related Art
Noncontainer pressurizing pump sprayers commonly utilize an integral cylinder and plunger arrangement to generate pressure to expel liquid, such as insecticide and fertilizer from a container. Noncontainer pressurizing pump sprayers are desirable in that they do not utilize pressurized containers which must be handled carefully and at controlled temperatures to avoid the risk of explosion. Noncontainer pressurizing pump sprayers have a number of other advantages, including not using propellants which destroy the ozone and being relatively inexpensive.
There are two common varieties of noncontainer pressurizing pump sprayers: pump sprayers that are pressurized on the upstroke and pump sprayers that are pressurized on the downstroke. Pump sprayers that are pressurized on the downstroke typically utilize a return spring which biases the plunger upward after the pressurization stroke. Examples of such noncontainer pressurizing pumps can be found in U.S. Pat. Nos. 4,174,055 and 6,296,154. While these arrangements have been successful, noncontainer pressurizing pumps are still relatively complicated and expensive devices. As such, there is a general need to develop noncontainer pressuring pumps that utilize fewer parts and/or can be made out of less expensive materials.